A direct, or open circuit Cooling
Towers in Pakistan is an enclosed structure with internal means to
distribute the warm water fed to it over a labyrinth-like packing or
"fill."
The fill provides a vastly expanded air-water interface for
heating of the air and evaporation to take place. The water is cooled as it
descends through the fill by gravity while in direct contact with air that
passes over it. The cooled water is then collected in a cold water basin below
the fill from which it is pumped back through the process to absorb more heat.
The heated and moisture laden air leaving the fill is discharged to the
atmosphere at a point remote enough from the air inlets to prevent its being
drawn back into the Cooling towers.
An indirect, or closed circuit Cooling towers involves no direct contact of the
air and the fluid, usually water or a glycol mixture, being cooled. Unlike the
open cooling tower, the indirect Cooling
Towers in Pakistan has two separate fluid
circuits. One is an external circuit in which water is recirculated on the
outside of the second circuit, which is tube bundles (closed coils) which are
connected to the process for the hot fluid being cooled and returned in a
closed circuit.
Air is drawn through the recirculating water cascading over
the outside of the hot tubes, providing evaporative cooling similar to an open
cooling tower.
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